I’m not an expert when it comes to color names used by AppleScript but maybe this may be a hint. I’m sure the AppleScript experts on this forum can tell you the exact reference for these color names.
In theory, yes. But every app has its own terminology. So you’ll have to make sure that it fits.
I’m not sure (I’m not scripting Pages, usually) but I think this can only be accomplished via UI scripting. If you are really interested in this I will write a macro for you. But, as always, UI scripting is the last recurse, and most of the time (or: many times) it will produce more problems than it solves.